CAMP GEIGER, N.C. — Their task: Complete a grueling 59-day test of physical and mental strength for a job long thought to be out of their reach.

Their reward: Credit in their career personnel file, and a place in U.S. military history.

Their identity: hidden, until one of them posted online an instantly iconic photo revealing their grinning faces to the world.

On Thursday morning, three female Marines — Pfc. Cristina Fuentes Montenegro, Pfc. Julia Carroll and Pfc. Katie Gorz — became the first women to graduatefrom the Marine Corps’ enlisted infantry training course at Camp Geiger, N.C. They were assigned to Delta Company, Infantry Training Battalion. A fourth woman, Pfc. Harlee “Rambo” Bradford, who was sidelined with a leg fracture, may join them in a few weeks if upon her recovery she can complete the program’s final Combat Fitness Test and Physical Fitness Test.

ITB, as Marines call it, is mandatory course for all enlisted personnel hoping to obtain an infantry military occupational specialty. It was opened to women this fall as part of the Marine Corps’ research to identify which additional ground combat jobs may lift their gender restrictions.

During a Thursday morning graduation ceremony, Lt. Col. Dave Wallis, the battalion’s commanding officer, congratulated the Marines — a graduating class of about 225 — on their achievement.

“I have two messages for you. The first is this: You are prepared,” Wallis said. “No matter where you go, the training you received will fare you well.”

The second message, Wallis said, was encapsulated in the iconic recruiting poster image of the Marine drill instructor bellowing “We never promised you a rose garden.”

“You have to fight for that job. You have to earn it,” he said. “Never stop challenging yourself, never stop moving forward.”

Fifteen female Marines reported to ITB on Sept. 24 alongside male counterparts. Seven women remained with Delta Company prior to the hardest physical challenge of the course, a backbreaking 12½-mile hike while weighed down with a 90-pound combat load. After the Oct. 28 challenge, four women remained.

Fuentes Montenegro, 25, said the ITB experience, though difficult, had brought her closer to the Marine Corps and members of the battalion.

“Our instructor, he told us all it takes is everything you got, and it’s true,” she said. “Once you are committed to a goal, you can make it if you put everything into it.”

Carroll, 18, downplayed the accomplishment.

“I don’t really feel anything special just because, [the male graduates] did the same thing that we did, and a lot of them did it better than us,” she said. “I don’t feel any different from them, I don’t think.”

Both women said the men in their battalion had accepted them and treated them with professionalism.

Gorz, 19, declined to be interviewed.

Pfc. Trent Wetzel, who also graduated from Delta Company, said he didn’t see a problem with the women training alongside the men, despite the controversy that has attended the move.

“Everyone has their own opinions,” he said. “Personally, I believe it’s fine. Training is training.”

Throughout ITB, the identity of the female volunteers was carefully guarded from media exposure to respect their privacy. But they were outed a few days ahead of graduation after Bradford posted a photo to her Instagram account showing the remaining women of Delta Company smiling into the lens.

“And then there was four,” the caption read.

While the women didn’t find out until later that the picture had been posted and gone viral, Fuentes Montenegro said the image stood for the sisterhood the women had shared.

Carroll and Fuentes Montenegro said the public attention had been unnerving at first, though they had gotten used to seeing reporters during their field exercises.

But Carroll said she was more interested in getting to her MOS school and taking on new challenges than becoming the public face of women in the infantry.

“I’m not interested in dwelling on the past,” she said.

Marine Corps infantry specialties remain closed to women; the three female ITB graduates will receive credit for the course, but report to non-infantry MOS schools for further training.

Gorz plans to pursue a logistics specialty; Fuentes Montenegro will train to be an aviation mechanic, and Carroll will train in signals intelligence.

But Carroll, whose father was a reconnaissance Marine, said she would absolutely choose an infantry specialty if given the chance.

“I wanted to be a mortarman,” she said. “It just seems cool.”

But the Marines continue to evaluate the possibility of opening infantry roles as part of the Pentagon’s Women in Service Restriction Review. The Corps plans to send 300 women through ITB by next fall, though officials have said they don’t plan to open any infantry fields before 2015 — and even then, the service could ask for an exception that would keep some jobs closed to women.

Carroll, Fuentes Montenegro, and Gorz may not be the only female graduates of ITB for long. Two more companies, Echo and Alpha, began training with the battalion in October. According to Wallis, nine of the 13 women who began with Echo company remain, and eight of nine remain in Alpha. Bravo company, which kicked off training Nov. 12, has yet to drop one of its 22 female volunteers.